The two have much in common as first-term senators elected with the help of the tea party from states with large Latino populations. Both have Cuban roots and are considered rising GOP stars and prospective presidential rivals. But the pair is divided on immigration legislation — a key difference that could have significant ramifications for their party and political ambitions.

The Texas freshman is sharply critical of the pathway to citizenship for the nation’s 11 million undocumented immigrants, a central part of the bipartisan bill that Rubio helped write. Cruz is weighing whether to aggressively oppose the immigration overhaul, a decision that could neutralize Rubio’s outreach to conservative activists in order to minimize their opposition.

Cruz hasn’t yet decided whether to become the face of the opposition. But if he does, the Texan could burnish his conservative credentials and establish himself as a right-wing foil to Rubio as well as Sen. Rand Paul (R-Ky.) — who has expressed support for legalizing undocumented immigrants — in a potential 2016 bid.

But if Cruz were to lead the fight against the comprehensive plan, it could also spark a revolt from the large — and growing — population of Texas Hispanics who opposed his candidacy in large numbers in 2012. Cruz’s thinking will be on fresh display Monday, when witnesses testifying before the Senate Judiciary Committee could be subjected to his prosecutorial style of questioning.

The Cruz-Rubio divide underscores the soul-searching within the GOP over immigration reform as Republicans continue to ask themselves: Should they soften their opposition to a comprehensive plan after witnessing a mass erosion of support from Latino voters in recent election cycles? Or should they stand firm and defeat any bill that could provide “amnesty” to millions of illegal immigrants and instead mainly demand tougher border security laws?

So far, Cruz has yet to emerge as the chief opponent of the Senate bipartisan proposal.

For now, the firebrand Texas conservative is launching a carefully calibrated critique of the bill, calling for a focus on consensus items like border security and changes to current law that would help legal immigrants enter the country more quickly — all the while attacking the proposed pathway to citizenship for those living here illegally.

Last week, Cruz repeatedly avoided talking to reporters about the newly unveiled immigration plan authored by Rubio and seven other senators, saying he was still reviewing it and was instead focused on fighting gun control legislation.

But speaking to a few reporters late last week in the Capitol, Cruz did raise concerns over the pathway to citizenship — even as he avoided calling it “amnesty,” as conservative critics are quick to do.

Cruz said he was still reading the bill, but if it is “conditioned” on a pathway to citizenship, it makes it “quite likely” Congress will defeat it.

“President Obama wants a political issue more than he wants to pass a bill,” Cruz said bluntly. “And I think that’s unfortunate. I think right now, the single greatest impediment of common-sense immigration reform passing is President Obama, because I think there’s a consequence of insisting on a path to citizenship: It makes it far more likely that immigration reform will be voted down altogether, and that would be a very unfortunate outcome.”

Asked if he thought Rubio had been duped by Obama into backing a bill with a pathway to citizenship, Cruz praised his fellow Republican for having “worked very hard” to produce the 844-page measure, which he said has some “good positive steps.”

Still, he quickly added this critique: “If the objective is to pass a bill, you don’t hold the positive areas of agreement hostage to areas of sharp disagreements.”

Cruz was one of the first senators to receive a briefing from Rubio even before the bill was officially released, a sign of how critical the Texas conservative will be as the Florida senator tries to shape conservative opinion.

“I briefed him on it and his staff, but I don’t think he’s prepared to support it — he’s got a lot of questions, and they’re legitimate questions,” Rubio said.

Rubio, meanwhile, has emerged as a vigorous defender of the bill, making the pitch to conservative talk radio and right-wing commentators that the bill would offer the toughest border enforcement measures in history. For illegal immigrants to obtain green cards after 10 years and citizenship after 13 years under the bill, those enforcement measures would have to occur — and immigrants would have to pay fines and taxes while undergoing criminal background checks.

Asked to respond to Cruz’s assertion that points of agreement shouldn’t be held “hostage” to the pathway to citizenship, Rubio said: “He hasn’t told me that — obviously, I’ve read his public comments on it — he told me he wanted to review the whole bill.”

Rubio has positioned himself as a potential 2016 candidate who can bring together warring factions of his party, whether it’s the GOP establishment or tea party activists. And his deal making on the immigration bill could position him well in a general election, which Democrats even privately acknowledge. Meanwhile, Paul — who has sought to expand his own profile beyond his libertarian and tea party base — has floated legalizing the nation’s undocumented immigrants as one way to help the GOP broaden its tent.

But Cruz is continuing to cater almost exclusively to the tea party and activist base of his party while maintaining a purist conservative voting record. And he’s made a mark in his early days in the Senate, battling Chuck Hagel’s nomination to the Pentagon and emerging as a fierce opponent of gun control legislation — while throwing sharp elbows at some of his colleagues, something uncommon for newly elected freshman senators.

“Every leading GOP 2016-er is supporting comprehensive immigration reform,” said one Texas Republican source who knows Cruz well and asked not to be identified. “The worst secret in D.C. is Cruz is going to run for president, and he’s going to lean in hard against immigration to separate himself from all other 2016-ers.”

Cruz and his aides strongly deny that political motives are driving his immigration stance. They argue that coming from a border state with security shortfalls means there is a demand for tougher enforcement measures to stem the tide of illegal immigration.

“He comes from a different state,” Sen. Orrin Hatch (R-Utah) said when asked about Rubio’s and Cruz’s diverging approaches to the issue so far. “There’s a difference between representing Texas and representing Florida.”

While Rubio is congenial toward Cruz, and their offices have worked together on a handful of issues, the Floridian’s advisers are watching the Texan closely and have recognized the political threat he represents since last summer’s Texas primary.

Asked if the state’s Latino electorate is eager to see a pathway to citizenship enacted, the senior GOP senator from Texas, John Cornyn, said: “I’m not sure you can generalize. Most of them are citizens. I think they’d like to see some resolution of the immigration issue.”

Last year, Cruz was losing the Hispanic vote by about 30 percent in a state where there were 4.4 million Latino voters last cycle, amounting to more than 27 percent of the electorate, according to polling conducted on the eve of the election by the firm Latino Decisions. Immigration was the second most important issue behind the economy for Latino voters in Texas, according to the firm.

In Florida, about 17 percent of voters were Latino during the 2012 cycle, amounting to about 2.1 million voters there, according to the Pew Research Hispanic Center. Rubio won 62 percent of the Hispanic vote in his 2010 election victory, driven in large part by Cuban voters, according to Latino Decisions.

Indeed, both the 41-year-old Rubio and the 42-year-old Cruz are of Cuban heritage, and both rode a tea party wave to help them secure the GOP nominations in their respective Senate primaries. Cruz, a Harvard-educated former Texas solicitor general with a Cuban father, was born in Canada. But since his mother was a U.S. citizen when he was born, it appears he is still legally eligible to run for president, though it remains an unsettled question.

Sen. Lindsey Graham (R-S.C.) praised Cruz for his tough stance against gun control legislation last week, but the two are about to be on opposite sides during the immigration debate.

“I like Ted, but it’s up to him” on immigration, said Graham, a co-author of the bill. “I believe America is ready for immigration reform because the alternative of doing nothing is amnesty. You got a better idea, put it forward.”

While he has so far avoided mounting much of a public push against a pathway to citizenship, Cruz did issue a statement in January calling the idea in the Senate plan “profoundly unfair” and “inconsistent” with the rule of law. Cruz warned Sean Hannity earlier this month that “legal immigrants” get “left behind” under legislation to establish a pathway to citizenship to those here illegally. And that came several weeks after Rubio had won praise from the conservative commentator for his approach to immigration legislation.

Asked last week if he was concerned that blocking the plan could hurt Republicans in future elections, Cruz demurred.

“I don’t think we should be making those decisions through a political lens,” Cruz said. “I think we should be working to do the right thing, to fix our broken immigration system, to secure our borders and to uphold the rule of the law.”